Most people are exposed to many types of undesirable acoustic disturbances every day in both indoor and outdoor environments. Such acoustic “noise” includes undesired audible sounds, but also mechanical vibrations or other acoustic disturbances as well. Common sources of acoustic noise include automobiles, airplanes, trains, motorcycles, lawn mowers, chain saws, construction equipment, ventilator systems and other industrial and commercial products. Typically, noise results from vibrations emanating from motors, blowers, pumps, fans or other components of such devices. In addition to being annoying to humans, different types of acoustic noise can affect the operation of vehicles (e.g. aircraft or seacraft) and other machines.
One technique for reducing the effects of noise, called “active acoustic damping”, involves providing an additional sound, tone or other vibration to effectively cancel the undesired noise at a particular location. Active damping is commonly used on many vehicles, as well as in many industrial or commercial settings. Commercial aircraft, for example, commonly use active damping techniques to reduce the level of noise in the passenger cabin emanating from aircraft engines and other sources. By providing an appropriate “canceling” tone at some point between the source(s) of the noise and the listener, the effect of the noise upon the listener can be effectively reduced. Typically, this canceling tone is provided by audio speakers or other vibrating devices located near the cabin, resulting in noise suppression throughout the passenger cabin. Alternatively, active damping can be provided by headphones or the like worn by passengers and/or crew members. Similar concepts are applied in other settings, including many industrial and commercial settings where excessive noise is present.
Conventional active damping techniques, however, typically require additional hardware (e.g. loudspeakers, tuning forks or other devices capable of producing an appropriate canceling vibration). This additional hardware can add undesirable bulk, weight and complexity to a vehicle or product. In certain implementations (e.g. aircraft, seacraft and the like), this excess weight and bulk can present significant design issues. Unmanned underwater vehicles (UUV), for example, typically require exceptional acoustic performance, yet have very stringent weight and volume requirements.
Accordingly, it is desirable to create an active acoustic damping technique that can be readily implemented without excessive additional hardware. Further, it is desireable to create systems and techniques that are capable of actively canceling acoustic reverberations in vehicles and the like without adding substantial weight or bulk. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the foregoing technical field and background.